Process for recycling steel bodymaker punch sleeves

ABSTRACT

A process for recycling tool steel or comparable alloy steel bodymaker punch sleeves utilized in manufacture of seamless cans comprising annealing worn punch sleeves; expanding the punch sleeve using explosives underwater; hardening the expanded punch sleeves by heat treatment; and, if necessary, reducing the inner location surfaces of the punch sleeve by plating or metallizing with acceptable metal; and grinding the locating surfaces, outside surfaces, nose, and ends of the punch to the specified size; and the rebuilt punch sleeves as articles of manufacture.

United States Patent [1 1 Hanson I [451 Oct. 30, 1973 PROCESS FOR RECYCLING STEEL BODYMAKER PUNCH SLEEVES Inventor: Ivor G. Hanson, Apt. 303 265 3rd Ave., Boulder, Colo. 80302 Filed: Mar. 27, 1972 Appl. No.: 238,632

U.S. Cl. 72/56, 76/107 Int. Cl. B2ld Field of Search 76/107 R, 107 A;

References Cited UNITED STATES PATENTS 7/1929 Opie et al. 29/401 2/1966 Kunsagi 29/421 Primary Examiner-Andrew R. Juhasz Assistant Examiner-William R. Briggs Attorney-Ronald F. Weiszmann [5 7] ABSTRACT A process for recycling tool steel or comparable alloy steel bodymaker punch sleeves utilized in manufacture of seamless cans comprising annealing worn punch 10 Claims, 6 Drawing; Figures ///////////AV///////// bfi,

PAIENTEDncI 30 1915 SHEET 1 BF 3 PROCESS FOR RECYCLING STEEL BODYMAKER PUNCH SLEEVES BACKGROUND OF INVENTION 1. Field of the Invention This invention relates to the field of recycling of steel, generally tool steel, and more particularly to rebuilding bodymaker punch sleeves utilized in drawand-iron processes for manufacturing seamless cans.

2. Prior Art The draw-and-iron process for manufacturing seamless cans from such metals as aluminum, steel, brass, or copper has been known for some time. This process incorporates a blanking and cupping operation followed by a redraw and ironing process. Metal coil stock is lubricated and fed into a cupping press where the coil stock is sheared into circular blanks and the blanks drawn into a cup. Such a process is shown in Coors Goes All-Aluminum, by Fred L. Church, Modern Metals Journal, Jan. 1972, pages 64-82. The cup is then fed into a bodymaker press where a punch sleeve attached to a ram rapidly moves the cup through a redraw ring and a series of ironing rings which stretch the cup to nearly three times its original diameter. At the bottom of the bodymaker stroke, the can body is stripped and domed. Various can sizes are produced in the draw-and-iron process. Bodymaker punch sleeves may produce from 300,000 to 1,500,000 cans depending upon metal wear allowances, lubrication, temperature, etc. Typical operating procedures require that the punch sleeves be utilized until the outside surface becomes scratched or exhibits excessive wear and/or excessive metal loss. The punch sleeve is sequentually reground and the exterior surface roughened to reestablish an acceptable surface. The punch sleeves are utilized. until approximately 0.0040.0l inches of metal has been removed from the outside diameter by wear and regrinding. Heretofore after the bodymaker punch sleeves have been worn down to the above mentioned sizes, they have been discarded or sold as scrap metal since no further use can be obtained from them. The usefulness of these items is limited by the can volume. A punch sleeve sequentually worn and reground to a diameter which produces a container of less than 12 fluid ounces is useless.

Attempts to recycle these bodymaker punches in the past have proved futile, and methods for re-enlarging the outside diameter by building with metal plating, sputtering or metallizing have likewise proved either uneconomical or technically unacceptable. Often these methods produce surfaces of deteriorated quality and result in cans of inferior quality and produce only fractional numbers of the cans produced by the original bodymaker punch sleeves.

With the recent emphasis on environmental problems, significant attention has been directed to such seamless cans. Of special interest is the aluminum can, a product of the draw-and-iron process, which can be easily and economically used in recycling processes whereby, used aluminum cans are remelted and processed into coil stock for reuse by can manufacturers. In the year 1971 the can industry consumed 500,000 tons of aluminum. It is estimated that this value will increase to 1 million tons by 1976. This contribution to solid waste is an ecological problem which is being solved by aluminum can recycle programs. With a significantly higher salvage value for aluminum than steel,

it is no wonder that the public is actively participating in the aluminum can reclcle program. As an example, Adolph Coors Company, Golden, Colorado, had a 25 percent return on their aluminum cans in 1971. It is estimated that the aluminum seamless. can will account for percent of the beer and soft drink cans in the United States within 10 years. The ecological benefit of recycling bodymaker punch sleeves in accordance with this patent is obvious.

In contrast to these attempts of the prior art, the present invention presents a novel and unique method for recycling steel, preferably tool steel, bodymaker punch sleeves for further and continued useability in seamless can production. Surprisingly, the process of the present invention may be used many times over on repreparation of the hardened tool steel punch. Punches reconditioned in accordance with the present invention exhibit the same life or wear rate as did the original bodymaker punch sleeves. In addition, the cost of reprocessing the punches is substantially lower than the cost of new punches, providing the necessaryeconornic emphasis for continued recycling. Further advantages will become evident in accordance with the following description.

SUMMARY OF DRAWINGS In order to more fully describe the invention, reference is now made to the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a typical bodymaker punch sleeve.

FIGS. 2, 3 and 4 are cross-sectional views of a bodymaker punch sleeve showing a sequential shot schedule of explosive charges underwater for enlarging the punch.

FIG. 5 is a cross-sectional view showing an explosive charge placed in a partitioned punch sleeve for expanding only a portion of the punch.

FIG. 6 is a cross-sectional view of a drawn-andironed can on the punch sleeve prior to being domed.

DETAILED DESCRIPTION OF DRAWINGS Referring to FIG. 1, the bodymaker punch sleeve comprises the outer surface, 1, the nose or front 2, and back 3 of the punch, the inner locating surfaces 4 of which there may be two or more, and the undercut area 5 (optional).

FIGS. 2, 3, and 4 show a sequence of explosive shot placements for expanding a bodymaker punch sleeve 6 underwater.

In FIG. 2, variable size continuous explosive charge 7 and 8 is placed along the center axis of the punch and exploded with detonator 9.

FIG. 3, shows a suitable placement of charge 7 and 8 after detonation in accordance with FIG. 2.

Likewise, FIG. 4 demonstrates a final distribution of an explosive charge depicted by an explosive ring charge 10.

Referring to FIG. 5, a bodymaker punch sleeve 6 is placed underwater 11 with air 12 between two partitions 13. An explosive charge 14 and detonator 9 are placed so that expansion is caused only in the back section of the punch.

Referring to FIG. 6, the following items can be seen: the bodymaker punch sleeve 6 positioned on a ram 15 with nut 16 and washer 17; a drawn-and-ironed can body 18 about to be contacted by domer l9.

DETAILED DESCRIPTION OF INVENTION The process of the present invention is directed towards recycling or rebuilding bodymaker punches in which the exterior diameters or surfaces have been so worn as to render them useless in the manufacture of the desired seamless can size. The worn punches are reprocessed by first softening by annealing at temperaures ranging from l,300 to l,700 F. and preferably from l,400 to 1,650 F. This heating may be accomplished by using means such as vacuum furnace, inert gas furnace, or salt bath furnace, etc., and preferably by using a vacuum furnace. After heating to the desired temperature range, the punch sleeves are cooled by reducing the temperature from a range of 15 to 50 F. per hour, and preferably 20 to 40 F. per hour. The heating, annealing and cooling of the tool steel is a critical step in assuring the rebuilding of the punch sleeve. The isothermal process of annealing the tool steel may also be utilized in accordance with the present invention. Failure to follow the prescribed conditions may result in inability to reprocess the tool steel as desired. In the hardened condition, the tool steel is extremely brittle with essentially percent elongation and easily fractures. The annealing process allows for a small amount of elongation or metal movement allowing the metal to be enlarged in accordance with the process of the present invention.

After the punch sleeve has been annealed, it is then expanded to the desired outside dimensions by utilizing class A or high velocity explosives having a detonation velocity of from 6,000 to 28,000 feet per second and preferably 20,000 to 25,000 feet per second. Preferably, the explosive is detonating cord such as primacord having a range of 18 to 100 grains per foot, and preferably 18 to 50 grains per foot.

The process of expanding the annealed sleeve comprises positioning a charge such as, a piece of primacord or detonating cord along the center axis of the punch sleeve. The positioning devices may be inexpensive cardboard or plastic to maintain the charge along the center axis to insure maximum and balanced expansion. After positioning of the charge inside the punch, a blasting cap and/or fuse are attached to the cord and the whole device is submerged in water. The explosive is then detonated while the punch sleeve is positioned underwater. The detonation under water allows substantially equal diametric expansion of the punch sleeve in all positions and the depth of water within practical limitations has little or practically no effect on the results.

After expansion, the outside diameter is measured to insure that it has been expanded to the desired size. Due to thickness and confinement of the explosive pressures generated, frequently the punch will not be expanded to the desired size with one charge. In addition, attempting to enlarge the punch with one large charge may result in cracking.

To overcome these problems systematic use of sequential charges as depicted in FIGS. 2, 3 and 4 is utilized. That is, the punch is expanded in a series of 2 or more smaller charges to produce the desired expansion.

In some cases, it is desirable to expand only one area of the punch and at the same time, prevent expansion in other areas. This maybe accomplished by using an air pocket as shown in FIG. 5. Partitioning of the punch to trap air between the partitions results in essentially zero expansion in the partitioned space.

After expansion the punch sleeve is hardened to a range of 38 to 66 and preferably 60 to 64 on the Rockwell C Scale. Methods for heat treating and hardening tool steel are commonly known in the art and these methods may be followed in the instant case.

The expansion of the punch sleeve results in the location surfaces 4 as shown in FIG. 2 being oversized. Consequently, it may be necessary to rebuild these areas and reduce the diameter in order to provide them with acceptable location surfaces to fit the existing bodymaker ram sizes upon which the punches fit. The surfaces are rebuilt to sufficient size to allow for grinding to tolerance levels. If larger diameter bodymaker rams are used it is unnecessary to reduce the diameter of the location surfaces.

Reduction of the size of the location surfaces is accomplished by plating them with such metals as hard chrome, nickel, or by metallizing with an acceptable metal such as molybdenum. Since it is not desirable to expand or reduce the size of the interior of the punch sleeve except for the location surfaces, the other areas are masked or other appropriate steps taken to reduce any unnecessary waste of metal, time, and effort. The inside surfaces are then ground to the desired tolerances and the outside surfaces are ground, polished, and roughened as required.

After preparation which includes annealing, expanding, hardening, plating, grinding, and surface preparation, the punch sleeves are then ready for reuse on the bodymaker press.

It is pointed out that the recycled or rebuilt punch sleeves do not meet the exact total dimensions of the original punch sleeve before being worn out; however,

the deviations which do exist do not alter the fact that the rebuilt punch sleeves can be utilized with no loss of can quality and efficiency within the prescribed limitations of the original punch sleeve. The process of the present invention may be used with or without a die or tooling backup.

EXAMPLE 1: A 7 inch long AISI M-2 tool steel punch with thicknesses varying from 0.30-'-0.22 inches along its length, an undercut section (see FIG. 2), and having a 2.5 inch outside diameter needed to be diametrically expanded 0.008 inches. The punch cracked after being subjected to a 50 grain per foot charge placed along its center axis. The crack emanated from the undercut area. The failure was caused by excessive internal pressure from too great a load.

EXAMPLE 2a: A similar M-2 tool steel punch was expanded approximately 0.020 inches on its diameter without cracking by using a sequence of shots of lesser explosive load. EXAMPLE 2b: An AISI 0-1 tool steel punch sleeve with a 0.45 inch thickness, 6 inches long and having a 2.6 inch outside diameter with no undercut area was exposed to a 50 grain per foot charge without failure.

When expanding thick-walled punch sleeves excessive external stress may be encountered prior to adequate diametric exapnsion which may result in external surface cracking. This cracking may be avoided by stress-relieving the punch sleeve after partial expansion of the punch and at a point before cracking occurs by heating in the range of from 1,000 to 1,600 F. and preferably from 1,200 to l,400 F.

EXAMPLE 3: An AISI M-2 tool steel punch sleeve having a major diameter of 2.4741 inches, a center wall thickness of 0.300 inches, and a length of 6.7 inches was utilized in a bodymaker press for manufacturing approximately 500,000, 12 ounce seamless aluminum cans. After wear and regrinding the outside major diameter was 2.4701 inches indicating a wearing of about 0.004 inches. At this point the sleeve was essentially useless for can making and it was subjected to the process of the present invention by annealing at a tempera-' ture of l,600 to l,650 F. and then cooled at a maximum rate of 40 F. per hour in a vacuum furnace. The punch sleeve was then expanded underwater by using primacord containing 25 to 50 grains per foot and was detonated with a blasting cap. The outside diameter was expanded to a minimum of 2.4770 inches and the location surfaces were enlarged by a minimum of 0.007 inches on the inside diameter. The expanded punch sleeve was then hardened using a vacuum furnace by preheating at l,025 F. for 30 minutes; heating at l,600 F. for 12 minutes, heating at 2,l50 F. for 5 to 6 minutes; quenching with nitrogen gas to 1,025 F. and stabilizing at 1,025 F. until the punch reached that temperature, air cooled to room temperature; tempered at l,000 F. for 3 hours; cooled at -l F. for 2 hours; tempered at l,O00 F. for 3 hours; and then air cooled to room temperature.

The two location surfaces were then chrome plated and their inside location surfaces were ground to the users specifications. The outside punch diameter, nose, and two ends were also ground and polished in accordance with the users specifications. The punch sleeve was ground to a major diameter of 2.4741 inches. The rebuilt punch sleeve differed in dimension from the original punch sleeve in the following specifms:

1. The inside diameters of the punch sleeve except for where it had been chrome plated were oversize 0.0050.014 inches.

2. The punch was undersize on length 0.018 inches. At this point the rebuilt punch sleeve was returned to use on a bodymaker press and has produced approximately 500,000 aluminum cans of excellent quality and dimension.

EXAMPLE 4: An AlSl M-2 tool steel punch sleeve having a major diameter of 2.5934 inches and center wall thickness of 0.356 inches was utilized in the process of preparing 500,000 to 700,000, 12 ounce seamless aluminum cans. After wear and regrinding, the outside major diameter was approximately 2.5900 inches and the entire outside surface of the punch had been worn 0.0034 inches on the diameters. At this point the punch was useless and it was subjected to the process of the present invention by annealing in a vacuum furnace at a temperature of l,600 to 1,650 F. and then cooled at a maximum rate of 40 F. per hour. The punch sleeve was then expanded underwater by using primacord containing 25 to 50 grains per foot and was detonated with a blasting cap. The outside diameter was expanded to a minimum of 2.5970 inches and the location surfaces were enlarged by a minimum of 0.007 inches on the inside diameter.

The expanded punch sleeve was then hardened using a vacuum furnace in the same manner as the punch sleeve described in Example 3.

The two location surfaces were then chrome plated and their inside diameter reduced by 0.014 to 0.016

inches. The inside and outside surfaces and the nose and two ends were ground, etc. in the same manner as described in Example 3. The major diameter of the punch sleeve afterprocessing was 2.5934 inches and the rebuilt punch sleeve deviated from the original punch sleeve dimensions in the same means as Example 3.

At this point, the rebuilt punch sleeve was returned to use on a bodymaker press in the preparation of 12 10 ounce seamless aluminum cans and has produced 900,000 cans of excellent quality and dimension.

EXAMPLE 5: An aircraft steel alloy E-52l00 punch sleeve of the same dimensions as EXAMPLE 4 was utilized in the process of making approximately 500,000, 12 ounce seamless aluminum cans. After wear and grinding the major outside diameter was approximately 2.5900 inches and the entire outside surface of the punch had been worn 0.0034 inches on the diameters. At this point the sleeve was useless and it was subjected to the process of the present invention by annealing in a vacuum furnace at a temperature of 1,400 to 1,45 0 F. and then very slowly cooled to room temperature. The punch sleeve was then expanded underwater by using primacord containing 25 to 50 grains per foot and was detonated with a blasting cap.

The expanded punch sleeve was then hardened by heating to 1,525 to 1,5 75 F. followed by quenching in oil at 140 F. The punch sleeve was then tempered at 350 F. for maximum hardness.

The two location surfaces were then chrome plated and the punch ground and finished in the same manner as Examples 3 and 4. The punch sleeve was ground to a major diameter of 2.5934 inches and the rebuilt punch sleeve deviated from the original punch sleeve dimensions in the same manner as Examples 3 and 4.

At this point, the rebuilt punch sleeve was returned to use on a bodymaker press in the preparation of 12 ounce seamless aluminum cans and has produced 500,000 cans of excellent quality and dimension.

It is to be understood that the forms of the invention as shown herein and described are to be taken as the preferred embodiment. Various changes may be made in the shape, size and arrangements of parts and equivalent elements such as metals, explosives, punch sleeves, etc. and may be substituted for those illustrated and described herein without departing from the scope and objectives of this invention.

' I claim:

1. A process for recycling cylindrical tool steel comprising:

a. annealing the tool steel at temperatures of from 1,300 to 1,700 F.;

b. cooling the tool steel at from 15 to 50 F. per

hour;

c. expanding under water the outside diameter of the tool steel by detonating a separate series of explosive charges placed along the center axis of the tool steel; and

d. hardening the tool steel.

2.A process as in claim 1 wherein at least one of the explosive charges is a ring charge.

3. A process as in claim 1 wherein the tool steel is a 5 bodymaker punch and after hardening the punch is processed as follows:

a. the location surfaces are reduced in size by plating or metallizing said surfaces; and

b. the outside and inside surfaces of the punch are ground.

4. A process as in claim 1 wherein the punch is:

a. annealed at temperatures of from 1,400 to l,650

b. cooled at a rate of 20 to 40 F. per hour;

c. the outside diameter is expanded using an explosive having a denotation velocity of from 6,000 to 28,000 feet per second and a grain load of 18 to 100 grains per foot;

d. the outside and inside surfaces of the punch are ground;

e. hardened from a range of 38 to 66 on the Rockwell C scale.

5. A process as in claim 3 wherein after at least one explosive expansion the tool steel is:

a. stress-relieved by heating at temperatures of from l,000 to l,600 F.;

b. expanded further by use of an additional explosive charge; and wherein steps (a) and (b) of claim 5 are repeated until the tool steel is expanded to the desired dimensions.

6. A process as in claim 3 wherein the detonation velocity is from 20,000 to 25,000 feet per second and the punch is hardened from 60 to 64 on the Rockwell C scale.

7. A process as in claim 4 wherein the explosive is a detonating cord having a grain load of from 18 to 50 grains per foot.

8. A process as in claim 4 wherein after at least one explosive expansion the tool steel is:

a. stress-relieved by heating at temperatures of from 1,000 to 1,600 E;

b. expanded further by use of an additional explosive charge; and wherein steps (a) and (b) of CLAIM 5 are repeated until the tool steel is expanded to the desired dimensions.

9. A process as in claim 8 wherein the detonation velocity is from 20,000 to 25,000 feet per second and the punch is hardened from 60 to 64 on the Rockwell C scale; and the explosive is a detonating cord having a grain load of from 18 to 50 grains per foot.

10. The product of the process of claim 4. 

1. A process for recycling cylindrical tool steel comprising: a. annealing the tool steel at temperatures of from 1,300* to 1,700* F.; b. cooling the tool steel at from 15* to 50* F. per hour; c. expanding under water the outside diameter of the tool steel by detonating a separate series of explosive charges placed along the center axis of the tool steel; and d. hardening the tool steel.
 2. A process as in claim 1 wherein at least one of the explosive charges is a ring charge.
 3. A process as in claim 1 wherein the tool steel is a bodymaker punch and after hardening the punch is processed as follows: a. the location surfaces are reduced in size by plating or metallizing said surfaces; and b. the outside and inside surfaces of the punch are ground.
 4. A process as in claim 1 wherein the punch is: a. annealed at temperatures of from 1,400* to 1,650* F.; b. cooled at a rate of 20* to 40* F. per hour; c. the outside diameter is expanded using an explosive having a denotation velocity of from 6,000 to 28,000 feet per second and a grain load of 18 to 100 grains per foot; d. the outside and inside surfaces of the punch are ground; e. hardened from a range of 38 to 66 on the Rockwell C scale.
 5. A process as in claim 3 wherein after at least one explosive expansion the tool steel is: a. stress-relieved by heating at temperatures of from 1,000* to 1,600* F.; b. expanded further by use of an additional explosive charge; and wherein steps (a) and (b) of claim 5 are repeated until the tool steel is expanded to the desired dimensions.
 6. A process as in claim 3 wherein the detonation velocity is from 20,000 to 25,000 feet per second and the punch is hardened from 60 to 64 on the Rockwell C scale.
 7. A process as in claim 4 wherein the explosive is a detonating cord having a grain load of from 18 to 50 grains per foot.
 8. A process as in claim 4 wherein after at least one explosive expansion the tool steel is: a. stress-relieved by heating at temperatures of from 1,000* to 1,600* F.; b. expanded further by use of an additional explosive charge; and wherein steps (a) and (b) of CLAIM 5 are repeated until the tool steel is expanded to the desired dimensions.
 9. A process as in claim 8 wherein the detonation velocity is from 20,000 to 25,000 feet per second and the punch is hardened from 60 to 64 on the Rockwell C scale; and the explosive is a detonating cord having a grain load of from 18 to 50 grains per foot.
 10. The product of the process of claim
 4. 